1. Field of the Invention
The present invention relates in general to a disk brake apparatus for motor vehicles and in particular to a hydraulic disk brake apparatus actuated through a hydraulic pressure generating system.
2. Description of the Prior Art
In a disk brake apparatus for motor vehicles such as two-wheel motor vehicles, a pair of brake pad assemblies are disposed in opposition to each other across an interposed brake disk which is mounted on an axle so as to be rotatable with an associated wheel. The brake pad assemblies are held movably relative to the brake disk by the respective arm portions of a caliper-like brake housing generally referred to as the caliper. One of the caliper arms is formed therein with a hydraulic cylinder chamber in which a piston is slidably diposed, whereby one of the brake pad assemblies is caused to bear against the brake disk when the piston is correspondingly moved under the hydraulic pressure produced in the cylinder, while the other brake pad assembly is subsequently brought into frictional engagement with the brake disk under the force transmitted to the associated caliper arm from the hydraulic cylinder in the manner well known to the art.
The hydraulic cylinder formed in the caliper arm is communicated to a master cylinder which constitutes a hydraulic pressure generating source and is adapted to be operated by a suitable means such as foot pedal. The master cylinder is provided separately from the cylinder formed in the caliper arm and is hydraulically communicated to the latter by way of a pipe line such as rubber hose or conduit of copper so that the hydraulic pressure produced in the master cylinder through operation of the foot pedal or the like may be transmitted to the cylinder chamber formed in the caliper arm so as to move the piston and hence the associated brake pad assembly toward the brake disk.
The hydraulic disk brake system of the arrangement described above is susceptible to various drawbacks. In the first place, because the master cylinder is provided separately from the disk brake apparatus, high expenditure as well as time consuming labour are required for the manufacture and installation of the master cylinder and associated parts or fixtures such as pipe line. Further, there may arise a loss in hydraulic pressure transmitted to the cylinder chamber in the caliper from the master cylinder because of flow resistance of communicating pipe line. Furthermore, a problem of leakage of hydraulic fluid may be involved. In certain application such as for two-wheel motor vehicles, a space available for mounting the master cylinder is restricted.